The Jamari River is a river of Rondônia state in western Brazil. Part of the river's watershed is covered by the 221218 ha Jacundá National Forest, a sustainable use conservation unit. The Jamari river is dammed by the Samuel Hydroelectric Dam near Porto Velho, which forms a reservoir that covers 56000 ha. The Samuel Ecological Station was established in compensation for the environmental impact. The ecological station extends to the east of the dam and protects part of the Jamari river basin.